US2237241A - Preparation of ethers - Google Patents

Description

' para-chloro-benzyl chloride, etc.

Patented Apr. 1, 1941 PREPARATIONOF ETHERS Charles J. Strosacker and Forrest C. Amstutz,

Midland, Mich., assignors to The Dow Chemical Company, Michigan Midland, Micln, a corporation of No Drawing. Application May 19, 1939,

Serial No. 274,590

7 Claims. (oi. 260-612) This invention concerns an improved method of making ethers having the general formula:

wherein R represents hydrogen or a monovalent aromatic radical.

In our co-pending application, Serial No. 247,678, filed December 24, 1938, of which this application is a continuation inpart, we have disclosed that polyhydric alcohols and hydroxyethers are catalysts for the alkaline dehydrohalo genation of halogenated aliphatic or alicyclic compounds containing halogen and hydrogen atoms on adjacent carbon atoms, to form corresponding unsaturated compounds. For example,

it is shown that such catalysts promote the reaction of sodium hydroxide with ethylene chloride to form vinyl chloride in accordance with the equation:

We have now found that polyhydric alcohols and hydroXy-ethers derived therefrom also accelerate the formation of ethers by the reaction of alkalies with halogenated organic compounds having the general formula:

wherein R represents hydrogen or a monovalent aromatic radical and X is a halogen. Such reaction for the formation of an ether is'illustrated i by the equation:

2RCH2X+2MOH- I RCH2OCH2R+2MX+H2O wherein M represents a metal.

In promoting this type of reaction, the polyhydric alcohol or its methyl chloride, methyl bromide, methyl iodide,

benzyl chloride, benzyl bromide, benzyl iodide, para-chloro-benzyl chloride, ortho-chloro-benzyl chloride, meta-chloro-benzyl chloride, orthopara-dichloro-benzyl chloride, para-bromoebenzyl bromide, ortho-methyl-benzyl bromide, paraethyl-benzyl chloride, meta-ethyl-benzyl chloride, para-isopropyl-benzyl bromide, ortho-methyl- The requisite of the reactant is that it shall contain no hydroaliphatic carbon atom adjacent to that carrying I the reactive halogen atom, since the presence of such adjacent hydrogen-bearing'carbon atom results in production of an olefine rather than an ether as the main product. 4

Among the various polyhydric alcohols and hydroxy-ethers which may be used to promote the reaction are ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, glycerine, 1.3-dihydroxy-propane, 1.3-dihydroxy-butane, 1.4-dihydroxy-butane, beta-ethoxyeethyl alcohol, beta-phenoxy-ethyl alcohol, beta-(2- chl0ro-phenoXy)-ethyl alcohol, beta-isopropoxyethyl alcohol, etc. Apparently any stable polyhydric alcoholo-r hydroxyether derived therefrom may be used for this purpose. I The ,glycols are :active catalysts, but hydroxy-ethers, e. g. polyglycols, are even-more eitective, Among the polyglycols, we haveobserved thatthe catalytic activity becomes greateras the number .of glycol residues (and therefore. ether, groups) ;in..the molecule. isincreased. For-instance, diethylene glycol is-a morea-ctive catalyst than. ethylene glycol; triethylene .glycol .is more. active than .diethylene glycol; .tetraethylene glycol is more active than triethyleneglycol,etc.-

.Sodium hydroxideis preferably-used asthe alkaline, reactant,- but, other alkalies capable of removing halogen from the organic reactant, e. g. potassium hydroxide, lithium hydroxide, etc., may be used instead.

Thealk-ali and organic reactant may beused in any desired. -proportions,-,but. the reaction 00.- curs most smoothlywhen av molecularexcess of the organic reactant islemployed as a medium ,for the reaction. Usually ,from ,1 to, 5 moles and preferably. between 2, and 4 moles of. the organic reactant is employed permole of thealkali, ,The catalyst may alsobe used in nearly any proportm put for sake ofeconomy'it is usually emto obtain reaction." The reaction usually occurs smoothly at ternperatui'"es between '50 *ahd"'150 C., but it may sometimesbe carried out at lower or higher temperatures. By using the more active of our catalysts, the reaction may in some On the other ride to form dibenzyl ether may be carried outat atmospheric or increased pressure, as. desired. Stirring of the mixture during the reaction is, of course, desirable.

The reaction is preferably carried out in the absence of diluents, but it may be carried out in the presence of a diluent, e. g. water or a monohydric alcohol such as methanol or ethanol, if desired. The benefits of the catalyst are obv tained regardless of whether or not a diluent is present.

After completing the reaction, the ether product is separated in conventional manner, e. g. by distillation. In those instances in which the ether formed by the reaction possesses a boiling point below that of the organic reactant used in its preparation, the ether may be distilled from the mixture during the reaction.

The following examples illustrate certain ways in which the principle of the invention has been applied, but they are not to be construed as limiting the invention.

Example I A bomb was charged with '77 grams (1.92

moles) of substantially anhydrous flaked sodium hydroxide and 158 grams (3.14 moles) of methyl chloride. The charge was heated with agitation at atemperature of 100 C. for 8 hours, The

bomb was then cooled and the organic products were distilled therefrom and condensed and collected in a trap cooled with an acetone-solid carbon dioxide mixture. The mixture of alkali and salt remaining in the bomb was analyzed, whereby it was found that only 57 per cent of the sodium hydroxide employed had been reacted. The organic distillate was analyzed and found to contain 80.5 per cent by weight of unreacted methyl chloride and 19.5 per cent of dimethyl ether.

Example 2 at atemperature of 100 C. for 8 hours, after which the organic product was distilled and the extent .of the reaction was determined as in Example 1. Analysis of the residue from the dis tillation showed that 83.3 per cent of the sodium hydroxide employed had been consumed. The

organic distillate was found to be practically pure dimethyl ether. It contained only 0.23 per cent by weight of unreacted methyl chloride.

Example 3 Two experiments on the production of dibenzyl ether were carried out under identical conditions, except that in one of the experiments a mixture of polyethylene glycols (largely diethylene glycol and triethylene glycol) was present as a reaction catalyst, whereas in the other experiment this catalyst was omitted. In the experiment using the catalyst, a mixture of 633 grams (5 moles) of benzyl chloride, 200 grams (5 moles) of flaked sodium hydroxide and grams of the polyethylene glycols was heated with stirring under reflux at atmospheric pressure to a temperature of 160 C. for 16 hours.

, The organic products were then distilled from the mixture and the residual mixture of salt and alkali was analyzed to determine the extent of reaction. It was found that 73.3 per cent of the sodium hydroxide employed had been consumed.

There were obtained grams (1.34 moles) of unreacted benzyl chloride and 348 grams (1.76 moles) of dibenzyl ether. The yield of dibenzyl ether was 96 per cent of theoretical, based on the benzyl chloride consumed. In the experiment carried out in the absence of the polyethylene glycols, but under otherwise similar reaction con-' ditions, only 24.4 per centof the sodium hydroxide employed was reacted.

In the following claims, the expression polyglyco where employed. refers generically to poly-alkyl'ene glycols, such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, dibutylene glycol, etc.

Other modes of applying the principle of our invention may be employed instead of those explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed,

We therefore particularly point out and distinctly claim as our invention:

1. In a method wherein an ether is prepared by reacting an alkali with a compound having the formula:

wherein R represents a member of the group consisting of hydrogen and mono-valent aromatic radicals and X represent a halogen, the step of carrying out the reaction in the presence of a catalytic amount of a compound selected from the class consisting of polyhydric alcohols and hydroxy-ethers.

2. In a method wherein an ether is prepared by reacting an alkali with a compound having the formula:

wherein R represents a member of the group consisting of hydrogen and mono-valent aromatic radicals and X represents a halogen, the step of carrying out the reaction in the presence of a hydroxy ether in amount not exceeding about 0.1 of the molecular equivalent of the alkali.

3. In a method wherein an ether is prepared by reacting an alkali with a compound having the formula wherein R represents a member of the group consisting of hydrogen and mono-valent aromatic radicals and X represents a halogen, the step of carrying out the reaction in the presence of a polyhydric alcohol in amount not exceeding about 0.1 of the molecular equivalent of the alkali.

4. In a method wherein an ether is prepared by reacting an alkali metal hydroxide with a compound having the formula:

wherein R represents a member of the group consisting of hydrogen and mono-valent aromatic radicals and X represents a halogen, the

step of carrying out the reaction in the presence of a polyglycol in amount not exceeding about 0.1 of the molecular equivalent of the alkali.

6. In a method wherein dimethyl ether is prepared by reaoting an alkali with methyl chloride, the step of carrying out the reaction in the presence of a compound selected from the class consisting of polyhydric alcohols and hydroxyethers, said compound being employed in amount not exceeding about 0.1 of the molecular equivalent of the alkali.

7. In a method wherein dibenzyl ether is prepared by reacting an alkali with benzyl chloride, the step of carrying out the reaction in the pres-v ence of a compound selected from the class consisting of polyhydric alcohols and hydroxyethers, said compound being employed in amount not exceeding about 0.1 of the molecular equivalent of the alkali.

CHARLES J. STROSACKER. FORREST C. AMSTUTZ.